One of the goals of designers of high performance gas turbine aircraft engines has been to achieve thrust through the use of vectoring exhaust nozzles. To achieve this goal, engine designers have sought to improve the convergent/divergent axisymmetric nozzle to incorporate thrust vectoring while retaining the benefits of the underlying nozzle. One such improvement, shown in U.S. Pat. No. 5,082,182 entitled "Thrust Vectoring Exhaust Nozzle" issued Jan. 21, 1992 to Bruchez, Jr. et al and incorporated herein by reference, discloses an axisymmetric nozzle which is capable of positioning the divergent flaps of the nozzle such that the divergent flaps are not symmetric with respect to the longitudinal axis of the divergent section of the nozzle, while the convergent flaps remain symmetric. Another vectoring nozzle, disclosed in U.S. Pat. No. 4,994,660 entitled "Axisymmetric Vectoring Exhaust Nozzle" issued Feb. 19, 1991 to Hauer and incorporated herein by reference, discloses an axisymmetric nozzle which is capable of positioning the divergent flaps of the nozzle asymmetrically with respect to the longitudinal axis of the divergent section of the nozzle. Here again, the convergent flaps remain symmetric.
The convergent sections of the aforementioned thrust vectoring nozzles are essentially the same as that of the non-vectoring convergent/divergent axisymmetric nozzle which is well known in the art. Accordingly, adequate sealing techniques for preventing the escape of exhaust gas through the convergent flaps during engine operation are well known.
In the divergent section, each of these prior art nozzles incorporates a plurality of circumferentially arranged divergent flaps. Each of the divergent flaps has a "gas side", the surface of the divergent flap exposed to the exhaust gas of the engine, and an "air side", the surface of the divergent flap opposite the gas side. Divergent seals are located between, and overlap, adjacent divergent flaps to prevent the escape of the exhaust gas through the gaps between the divergent flaps. However, because the divergent flaps of these vectoring nozzles can move both radially and laterally, the prior art seals for the divergent section do not provide the desired sealing during the vectored exhaust condition.
In the aforementioned vectoring engines, all of the divergent flaps move in the same direction relative to the longitudinal axis of the divergent section during vectoring of the nozzle. This causes some of the divergent flaps to become radially offset relative to adjacent divergent flaps, while the trailing edges of other divergent flaps become axially offset relative to adjacent divergent flaps. Consequently, when the nozzle is in the vectored condition, the divergent seals must be able to twist up to twenty degrees or more along its length to maintain adequate sealing contact with the adjacent divergent flaps. Additionally, at both vectored and non-vectored conditions, the divergent seal must also remain centered between adjacent divergent flaps to ensure that the seal spans the entire gap between the adjacent divergent flaps.
What is needed is a device for positioning of the divergent seals that can tolerate the axial and radial offsets of the divergent flaps while ensuring that the sealing surfaces of the seal sealingly contact the adjacent divergent flaps at both vectored and non-vectored nozzle operating conditions.